High Performance Plus Solar

For reducing dependence on fossil fuels, solar is everyone’s darling, but when it comes to using it as a trade-off for a high-performance envelope, it loses its shine.

Blame it on the successful marketing campaigns of the solar industry. Homeowners and builders alike have been taught: It’s free! It’s infinite! It’s green! And, indeed, solar and other renewables are a huge game changer in the bid to free ourselves from dependence on fossil fuels.

But now solar is strapped to the hot seat during the 2018 IECC debates. Energy efficiency advocates are lobbying heavily to make sure that the new code doesn’t allow builders to weaken the building envelope simply by popping some solar panels on rooftops.

This issue became heated at the preliminary hearings in April, particularly over the inclusion of the RESNET/ICC Standard 301, which would make the HERS rating a path to code compliance. This worries energy-efficiency advocates who point out that the HERS calculation offers the ability to factor on-site power production into the score, which in turn means that unless states put limits on solar being used as a trade-off for performance, builders would indeed be allowed to weaken the thermal envelope.

ERI Vs. HERS: The Back Story

The 2015 IECC established the Energy Rating Index (ERI) compliance alternative, which is modeled after RESNET’s HERS. In order to comply with the IECC under the ERI path, the proposed home must have an ERI value equal to or less than the target established by the code. While the ERI compliance path has similarities to HERS (such as the similar 0 100 scale for setting the Index number), the HERS ratings have been used for green marketing of new homes and therefore offer the capability to include on-site power production in the calculation of the final HERS rating.

In contrast, the ERI number is intended to measure energy conservation to meet an energy efficiency compliance target, not energy purchased by the homeowner after conservation and self-generation are considered, and it sets climate zone specific targets for ERI performance path compliance.

According to the Florida Building Commission in an April memo: “A plain reading of the 2015 IECC should suggest that if HERS software is used to produce [a calculation] for ERI compliance, the code user must omit the final step that would include on-site power. States adopting the 2015 IECC must provide specific guidance on this point to ensure that energy conservation requirements are implemented fully and are not substituted by on-site energy production.”

If they don’t omit the on-site power piece, says the organization, here’s an example of the result: A typical Florida home with 5 Kwh of solar PV and 2,400 square feet would be awarded in excess of 40 HERS compliance points. If this were permitted as a trade-off against energy efficiency, the home could be significantly less efficient than what the energy code would allow.

Related: Solar Vs. Thermal Envelope Case Study: Florida

“The goal of our residential building code should be net zero energy ready homes, and the ERI compliance path, adopted in the 2015 IECC, is the likely approach by which to measure that goal,” says Curt Rich, president and CEO of the North American Insulation Manufacturers Association (NAIMA). “Unfortunately, the software tools used to calculate a home’s ERI score exceed the scope of the energy code and allow on-site generation to substitute energy conservation when calculating a score. That’s a fatal flaw in the ERI performance path, particularly when rooftop solar panels can generate upwards of 40 points toward a passing grade of 51-54, depending on climate zone.”

RESNET stayed neutral on the renewables topic at the preliminary code hearings in April, primarily because its focus was lobbying for the inclusion of Standard 301 in future versions of the IECC, which RESNET Executive Director Steve Baden, says “will simplify code language by striking duplicate provisions and ensures that the ERI approach is deployed using a standardized process from a consensus document.”

According to Baden, the 2015 IECC’s ERI isn’t based on any recognized standard, while the proposed RESNET/ICC Standard 301 is an ANSI national consensus standard. “The provisions of standard 301 are consistent with the 2015 IECC Energy Rating Index provisions including the development of the Energy Rating Index, compliance software tool approval, and the minimum capabilities of the software used to determine an ERI for a project.”

The ANSI/RESNET/ICC Standard 301 is a whole house assessment of a home, which includes onsite power production. “Standard 301 will continue to be a whole house assessment because it drives HERS Ratings,” Baden continues. “You cannot get to net-zero without onsite power production. As for it, there are reasonable arguments that there should be a limit on how much onsite power production can be credited for the ERI option.”

No Quarter

For some in the industry, though, any trade-off of the envelope for solar is taking energy efficiency backwards and should not be allowed at all.

“If you look at California in isolation, the requirement for performance for energy efficiency is higher than everyone else relative to 2015 codes,” notes Ron Jones, president of Green Builder Media. “In order for us to reach the requirements of California, leave the building envelope alone, at worst, and then add renewables, instead of setting it up as either/or.”

Jones believes that the only people manipulating the codes are the large production builders, such as Lennar, whose wholly owned subsidiary sells solar panels. “They put a deal in place that weakens the envelope and then have someone else [the homeowner] pay for the solar system. This isn’t about solar versus the envelope; it’s about the national builders.”

Laura Urbanek of the National Resources Defense Council (NRDC) points out that a well-built envelope creates a resilient home, which is another reason renewables and high-performance shouldn’t be an either/or proposition. “Hopefully buildings will last for 100 years. We need efficiency that can persist over that time” she says. “Efficiency is cost effective for the home owner and can be combined with renewables, but there’s no need to have one versus the other.”

Unsure Fate

301 made it through the first round of code hearings, but nothing is inked yet. “[301] had a lot of support on the floor,” says Erik Makela of Cadmus, who consults for RESNET. “In the hearings, the discussion of renewables came up before the 301 discussion, and [taking renewables out of the code] got overturned. So ultimately when 301 came up there was opposition from the groups who were against the renewable trade-off. We know there will be people at the hearings who will try to overturn the committee’s decision on it but from the RESNET perspective, 301 is a vetted standard. ICC even put their name on it.”

It appears that, as Baden said, barring either side winning outright, the middle ground may lie in creating limits on how much onsite power production can be credited for the ERI option—though even that would be considered a loss by energy-efficiency advocates.

“This is an issue where the old adage, ‘let’s not put the cart before the horse,’ applies,” Rich says. “While net zero energy homes necessarily require the use of renewables, it is the building energy code that ensures energy efficiency has been optimized to make that home net zero energy ready. It is our hope that the 2018 ICC residential code update process will put the focus back on the ‘horse’ of energy cost savings for the homeowner – that means focusing on energy efficiency.”

Related: Why You Shouldn’t Trade Thermal Envelope for Solar

Cati O’Keefe is the editorial director of Green Builder Media and the editor of Code Watcher. Contact her at cati.okeefe@greenbuildermedia.com.

1 Comment on "High Performance Plus Solar"

  1. Also, an Energy Efficient building is also better suited for Demand Response.

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